Time and Distance Bases. 491 velocity for the given position of crank, while the crank arm itself gives W's velocity. Taking various positions of P on HJ, and setting up the corresponding polar radii, the curve of P's velocity is obtained as H K j, while the ordinates A w, set up dotted on a base N o of half crank circle circumference, shew crank velocity. 4 Assuming P's pressure as uniform, the ordinates Im will give a curve of pressure; and the AE ordinates, being transferred from the polar curve to the base N o,. will give a curve of tangential pressures on crank. Notice points Q R and s T, where P and W have equal velocities, and also points F and w, where P has its highest velocity, and W its greatest pressure Time and Distance Bases.—The pfofile of velocity curve depends on the terms in which we state the base-line divisions. The curves in Fig. 434 are drawn with a time base line (equal titties), but the oblique lines at c and D -would be parabolas if a distance base (equal distances) were used. In Fig* 453, K j is a distance base, but supposing NO to represent L I.